Vertical axis wind turbine

ABSTRACT

The present invention provides a prime mover ( 2 ) for harnessing energy from a flow of fluid, the prime mover ( 2 ) comprising a shaft ( 4 ) having a rotational axis, arranged to be rotatably mounted to a substructure, the shaft ( 4 ) comprising at leas one arm ( 6 ) extending radially from the shaft ( 4 ), the or each arm ( 6 ) comprising at least one blade ( 8 ) wherein the or each blade ( 8 ) is oriented such that flow action on the blade ( 8 ) effects rotation of the shaft ( 4 ), characterized in that the or each blade ( 8 ) is movably mounted on an arm ( 6 ) and wherein each blade ( 8 ) is movable from a first position, having a first drag, to a second position, having a second drag, wherein the first drag is higher than the second drag. The prime mover ( 2 ) of the invention provides substantially reduced drag in a flow of fluid, and an increased torque output, compared to prior art prime movers.

TECHNICAL FIELD OF THE INVENTION

[0001] This invention relates to a prime mover, and in particular to aprime mover which harnesses energy from a flow of fluid. The inventionalso extends to a method of generating energy and an energy-generatingdevice.

BACKGROUND OF THE INVENTION

[0002] Renewable and non-polluting sources of energy are currently inhigh demand. Traditional sources of generating energy such as thecombustion of fossil fuels, including coal, natural gas and oil, arebecoming less and less favored due to their environmental disadvantagesThe combustion of coal, oil or gas generates large quantities of carbondioxide, oxides of sulfur and nitrogen, and other pollutant gases, whichmay contribute to global warming, acid rain, air pollution and a numberof other environment and health damaging effects. World reserves ofcoal, oil and natural gas are also thought to be relatively low, and mayrun out in the foreseeable future.

[0003] Other sources of energy include nuclear fission, whereby atoms ofradioactive elements are bombarded with a neutron source, which splitsthe radioactive element into an element or elements of smaller atomicmass, generating massive quantities of energy in the process.Unfortunately, the use of radioactive materials means thatenvironmentally safe methods of disposal of waste are difficult toachieve. The radioactive waste generated is commonly stored in sealedcontainers and then buried in restricted access landfill sites or dumpedat sea. There have been many occurrences of radioactive waste leakingfrom these containers and damaging the local environment. The damagecaused by radioactive waste may be irreversible and the radiationgenerated by the waste may last decades.

[0004] Thus, there is a strong desire to produce non-polluting andrenewable energy sources. Known non-polluting and renewable energyresources include tidal-powered electricity generators, and wind-poweredelectricity generators. These types of generators generally employturbine blades extending from a central hub, and which blades aredesigned to translate the linear motion of wind or tidal water intorotational motion of the central hub, which is connected to a suitableenergy generator. Known generators of this type generally employ turbineblades which are rigidly fixed to the central hub and are orientatedsuch that leading blades are aerodynamically configured in the optimalposition to convert fluid linear motion into rotational motion. However,this configuration of fixed blades means that trailing blades are notoptimally configured to reduce drag and thus prevent the maximum amountof linear to rotational motion available to generators. Thus the optimalconversion of linear to rotational motion may not be achieved usingthese known systems, and consequently, optimal energy generation is notpossible.

[0005] It is an aim of preferred embodiments of the present invention toovercome or mitigate at least some of the disadvantages of the prior artsystems described above, or other disadvantages, whether described aboveor not.

SUMMARY OF THE INVENTION

[0006] According to the present invention there is provided a primemover for harnessing energy from flow of a fluid, the prime movercomprising a shaft having a rotational axis, arranged to be rotatablymounted to a substructure, the shaft comprising at least one armextending radially from the shaft, the or each arm comprising at leastone blade, wherein the or each blade is oriented such that fluid flowacting on the blade effects rotation of the shaft, characterized in thatthe or each blade is movably mounted on an arm and wherein each blade ismovable from a first position, having a first drag, to a secondposition, having a second drag, wherein the first drag is higher thanthe second drag.

[0007] Suitably the flow of fluid effects movement of the or each bladefrom the first to the second position as the shaft is rotated.

[0008] Preferably the surface area of the or each blade impinged on bythe fluid is greater in the first position than in the second position.

[0009] Preferably the flow of fluid effects movement of the or eachblade from the second position back to the first position as the shaftcompletes a full rotation.

[0010] The prime mover may comprise two arms extending radially from theshaft, but preferably comprises at least three arms, more preferably atleast four arms, still more preferably at least five arms and mostpreferably at least six arms.

[0011] Suitably there are at least two arms, and at least one blade isin the second position when at least one other blade is in the firstposition.

[0012] Thus, in preferred embodiments, impingement of a blade by thefluid when in the first position effects rotation of the shaft As theshaft rotates the blade is oriented such that the flow of fluid movesthe blade from the first position to the second position, in which thereis lower drag. As the blade moves towards the second position, anotherblade on another arm moves into the first position whereby waterimpinging on said blade causes further rotation of the shaft. The bladein the second position, having a lower drag than the blade in the firstposition, reduces the drag on the prime mover than would otherwise beaffected by non-movable blades, and hence, effects increased torqueoutput of the prime mover.

[0013] Suitably each blade and/or arm comprises means to limit movementof each blade on an arm to a prescribed amount. Preferably, the movementlimiting means is arranged to limit movement of each blade on an arm tobetween the first and second positions.

[0014] Preferably each blade is rotatably mounted to an arm such thatthe blade may be rotated from the first to the second position. Suitablyeach blade is rotatable about an axis running substantially parallelwith the rotational axis of the shaft. Preferably the movement limitingmeans is arranged to limit rotation of each blade to a prescribedangular displacement, more preferably to limit rotation of each blade tobetween the first and second positions.

[0015] Preferably each arm and/or blade comprises means to prevent eachblade moving between the first and second positions until the shaft hasrotated a prescribed distance.

[0016] The means to prevent each blade from moving between the first andsecond positions until the shaft has rotated a prescribed angulardistance, and the movement limiting means, may comprise the same means.Suitably the prescribed distance is at least 90°, preferably at least120° and more preferably at least 150°. Preferably the prescribeddistance is no more than 180°.

[0017] Suitably the angular displacement between each adjacent arm issubstantially Identical. Thus when only two arms are present, the armsare suitably diametrically opposed about the rotational axis of theshaft.

[0018] Each arm may comprise more than one blade, each blade beingpreferably movably mounted on the arm. The blades are suitably mountedat prescribed intervals extending along the arm. The blades may overlap.Alternatively, the blades may be mounted superposed at one region of thearm. When the blades are mounted superposed at one region of the arm,there may be a separate movement limiting means for each blade or asingle movement limiting means to limit movement of all blades on anarm, to a prescribed amount.

[0019] The or each blade may comprise any suitable configuration whicheffects a higher drag in the first position than in the second position.The or each blade may comprise an elongate member having front and backsubstantially planar rectangular surfaces and having a substantiallywedge-shaped cross-section, kite-shaped cross-section, rectangularcross-section, lozenge-shaped cross-section, or airfoil-shapedcross-section. The or each blade may have a trim tab attached to theblade tip or blade trailing edge, partly or completely spanning theblade tip or blade trailing edge.

[0020] Suitably the prime mover is arranged to be rotatably mounted toany suitable sub-structure, such as an energy-generating apparatusincluding a dynamo electricity generator, with or without an attachedgearbox.

[0021] Suitably the prime mover is arranged to be rotatably mounted on asub-structure such that the rotational axis of the shaft issubstantially vertical with respect to ground level.

[0022] Suitably the fluid is air or water. Thus the prime mover may beused as part of an air-powered generating system, such as a wind-poweredgenerator, a tidal-powered energy generating system or an energygenerating system powered by the flow of river water.

[0023] According to a second aspect of the present invention there isprovided an energy-generating device comprising a prime mover asdescribed hereinabove, connected to an energy generating apparatus.

[0024] Suitably the energy generating apparatus is an electricitygenerator of any suitable type, which can convert rotary motion of theshaft of the prime mover, to electricity generation.

[0025] Preferably, the energy generating apparatus is a dynamo, with orwithout an attached gearbox. According to a third aspect of the presentinvention there is provided a method of generating energy from flow of afluid, the method comprising mounting the prime mover describedhereinabove to a suitable energy generating device and locating theresultant apparatus in a flow of fluid.

[0026] Suitably the prime mover is oriented in the flow of fluid suchthat the rotational axis of the shaft is oriented substantiallyvertically with respect to ground level and the arms extend radiallysubstantially horizontally with respect to ground level.

[0027] Suitably the prime mover mounted to the energy generatingapparatus, is located in a flow of air or water.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] For a better understanding of the invention, and to show howembodiments of the same may be carried into effect, reference will nowbe made to the accompanying diagrammatic drawings in which:

[0029]FIG. 1 illustrates a perspective view of a preferred embodiment ofthe prime mover of the invention.

[0030]FIG. 2 illustrates a plan view of the preferred embodiment of theprime mover shown in FIG. 1.

[0031]FIG. 3 illustrates a perspective view of a second preferredembodiment of the prime mover of the invention.

[0032]FIG. 4 Illustrates a plan view of the second preferred embodimentof FIG. 3.

[0033]FIG. 5 illustrates a perspective view of a third preferredembodiment of the prime mover of the present invention.

[0034]FIG. 6 Illustrates a perspective view of a fourth preferredembodiment of the prime mover of the present invention.

[0035]FIG. 7 illustrates a perspective view of a fifth preferredembodiment of the prime mover of the present invention.

[0036]FIG. 8 Illustrates a perspective view of a sixth preferredembodiment of the prime mover of the present invention.

[0037]FIG. 9 illustrates a plan view of the sixth preferred embodimentof FIG. 8, and

[0038] FIGS. 10A-10G illustrates perspective views of preferred bladeshapes of the prime mover of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

[0039] Referring firstly to FIGS. 1 and 2 a preferred embodiment of aprime mover 2 comprises a shaft 4, which is cylindrical and has an axisof rotation running through its center. The shaft 4 comprises eight arms6 which extend radially from the shaft 4, with each adjacent arm havingan angular displacement of 45° from the next arm.

[0040] Each arm 6 comprises at its distal end, a blade 8. Each arm 6,comprises an upper 10 and lower 12 members, with each blade 8 beingpivotably mounted between the upper 10 and lower 12 members by way of apivot 14. Each arm further includes means to prevent each blade frommoving between the first and second positions until the shaft hasrotated a prescribed amount, said means comprising a retention bar 16spanning the space between the upper 10 and lower 12 members.

[0041] Use of the preferred embodiment of FIGS. 1 and 2 will now bedescribed.

[0042] In use, the shaft 4 is rotatably mounted on a suitable energygenerating apparatus, such as a dynamo electricity generator (notshown). Once mounted, the entire apparatus is positioned in a flow offluid, such as in a stream of air or under water in tidal or river flow.

[0043] The prime mover may have braking means (not shown) in order toprevent rotation of the shaft 4 in the flow of fluid, until desired.

[0044] In FIGS. 1 and 2, fluid flow is shown as moving in a prescribeddirection across the prime mover. In this embodiment, blades are movablebetween a first position labeled “A” in which the front surface 18 ofthe blade 8 is substantially perpendicular to the fluid flow, andpresents substantially the greatest surface area for fluid impingementand the greatest drag, to a second position “B” in which the frontsurface 18 of the blade 8 is substantially parallel with the flow offluid, and wherein the blade 8 presents substantially the smallestsurface area for fluid impingement, and the least drag.

[0045] It will be appreciated by the skilled reader that between thefirst position “A ” and the second position “B” the blades will presentdiffering sized surface areas for impingement of the fluid and differingdrag, these intermediate positions are labeled “A-B”.

[0046] As fluid flows, the fluid will impinge on the blades 8 in thefirst position “A”. The pressures of the flow of the fluid on the blades8 in the first position “A” causes rotation of the shaft 4, about thecentral axis. In this embodiment the shaft 4 is rotated clockwise. Whenthe blades 8 are in the first position “A” they are prevented from beingpivoted anti-clockwise between the upper 10 and lower 12 members of thearms 6 by the Retention bars 16.

[0047] The rotational movement of the shaft 4 can then be converted intoelectrical power or other power by the energy generating apparatus (notshown) to which the shaft 4 is connected.

[0048] As the shaft 4 is rotated, the arms 6 are also rotated, whichmovement begins to move the attached blades 8 from the first position“A” to the second position “B”.

[0049] Before reaching the second position “B” the blades 8 move throughintermediate positions labeled “A-B” whereby the front face 18 of theblades 8 moves from being substantially perpendicular to the flow offluid to being substantially parallel with the flow of fluid, with thetip 22 of the blades 8 oriented towards the flow of fluid. Furtherrotation of the shaft 4, causes the blades 8 in position “A-B” to orientsuch that the rear face 20 of the blades 8 begins to face the flow offluid, and thus begins to be impinged by the flow of fluid.

[0050] As the rear face 20 of the blades 8 is impinged by the fluid thepressure of the fluid forces the blades 8 to rotate around the pivot 14into the second position “B”. In the second position “B” the tip 22 ofthe blades 8 is oriented away from the flow of fluid and the front 18and rear 20 faces of the blades 8 extend substantially parallel with theflow of fluid.

[0051] Thus, in the second position “B” the surface area of the blades 8impinged by the flow of fluid is much smaller than in the first position“A” and hence the drag of the blades 8 is much reduced. Thus, the bladesin the second position “B” help to reduce the overall drag of the blades8 on the rotation of the shaft 4 and therefore reduce loss of energybetween the linear fluid movement and rotational movement of the shaft4.

[0052] The arms 6 continue to move as the shaft 4 rotates back to itsoriginal position. As the shaft 4 rotates to its original position theblades 8 in the second position “B” are forced by the flow of fluid topivot back towards the arm 6 to which it is connected and abut theretention bar 16. The blades 8 are then moved back to the first position“A” as the arms 6 are rotated further.

[0053] Thus, continual flow of fluid across the prime mover 2 effectscontinual rotation of the shaft 4 as the arms 6 are rotated and theblades 8 are move from the first position “A” to the second position “B”and back again.

[0054] Referring now to FIGS. 3 and 4, a second embodiment of the primemover 2 of the invention includes all the elements of the embodimentdescribed for FIGS. 1 and 2, but include means 24 to limit the movementof the blades 8 to between the first and second positions (“A” and “B”respectively) only. The movement limiting means 24 comprises an upper 26arm and lower 28 arm extending obliquely from each arm 6 of the primemover 2. The upper arms 26 and lower arms 28 include upper slots 30 andlower slots 32 respectively. The movement limiting means 24 furthercomprises guide rods 34, which extends through the blades 8 of the primemover 2 into the upper 30 and lower 32 slots of each movement limitingmeans 24.

[0055] In use the guide rods 34 cooperate with the upper 30 and lower 32slots to limit movement of each blade to between the first position “A”and the second position “B” as shown in FIG. 4. In the first position“A” the guide rod is located at the proximal end of the upper 30 andlower 32 slots of the movement limiting means 24. As the shaft 4 of theprime mover 2 is rotated, and the blades 8 are moved from the first “A”to the second “B” positions, the guide rod 34 is moved towards thedistal end of the movement limiting means 24 between the upper 30 andlower 32 slots.

[0056] The distal ends of the upper 30 and lower 32 slots are closed toprevent the guide rod 34 from leaving the movement limiting means 24.Thus, when the blades 8 reach the second position ‘B’ the guide rods 34prevent the blades 8 from rotating further. As the arms 6 rotate furtherand the blades 8 move back to the first position ‘A’ the guide rods 34moves back towards the proximal end of the movement limiting means 24.

[0057] The movement limiting means 24 prevent the blades 8 from beingmoved away from the second position ‘B’ when the minimum of drag isrequired on the blades 8, and thus prevents minimum drag configurationand instead adds torque to the prime mover 2.

[0058] In an embodiment such as that described in FIGS. 1 and 2, theabsence of movement limiting means 24 allows each blade 8 to achievesubstantially minimum drag when rotated to position B. This minimum drageffects negative torque on the prime mover, which is subtracted from thepower generated by the prime mover 2.

[0059] In case of embodiments, such as those of FIG. 3, in whichmovement limiting means 24 are present, the movement limiting means 24allow each blade to retain an impact angle against the fluid flowthrough a smaller angular displacement, which causes each blade 8 toform an oblique angle to the fluid flow for a longer time period and addto the torque of the prime mover.

[0060] Referring now to FIG. 5 in a third embodiments of the prime mover2 of the invention, only two arms 6 are shown, each arm 6 comprising asingle elongate member 36.

[0061] Each elongate member 36 comprises a retention bar 16, whichextends above and below the elongate member 36. Blades 8 are pivotablyconnected to the arms 6 by way of pivots 14. The prime mover 2 of thethird embodiment works in substantially the same manner as the firstembodiment described for FIGS. 1 and 2. The blades 8 of this embodimentare oriented to be retained in the first position ‘A’ by the retentionbars 16, above and below the elongate members 36.

[0062] Referring to FIG. 6, in a fourth embodiment of the prime mover 2of the invention, each arm 6 comprises two blades 8, spaced apart alongthe arm 6. Each arm comprises two retention bars 16, one for each of theblade 8. Each blade comprises its own pivot 14 and is independentlymovable from the first position ‘A’ to the second position ‘B’ as eacharm 6 rotates with the shaft 4. In this fourth embodiment blades 8 areindependent from the other, but in another embodiment (not shown), theremay be a blade link rod (not shown) connecting all blades 8 of the samearm 6 so as to make the blades move in unison.

[0063] The mode of the operation of the fourth embodiment issubstantially identical to that described on the embodiment of FIGS. 1and 2.

[0064] Referring now to FIG. 7, in a fifth embodiment of the prime mover2 of the invention, each arm 6 comprises two blades 8, which aresuperposed. Each arm 6 comprises upper 38 and lower 40 retention bars,to retain each of the blade. Each blade 8 comprises its own pivot 14,but in another embodiment (not shown) there may be a single pivotrunning through both blades. The mode of operation of the fifthembodiment is substantially identical to that described for theembodiment of FIGS. 1 and 2.

[0065] Referring now to FIGS. 8 and 9, a sixth embodiment of the primemover 2 of the invention includes all the elements of the embodimentdescribed for FIGS. 3 and 4, but now include a trim tab 42 attached tothe blade 8 trailing edge or tip 22 of each blade 8 to provide finetuning adjustment to increase blade efficiency. The trim tab 42, eitherwelded, riveted, or a plate integral part of blade 8, partly spanning orextending fully to cover the whole length along the blade 8 trailingedge or tip 22.

[0066] In use, the trim tab 42 alters the blade 8 attitude withreference to the fluid flow every time blades 8 guide rods 34 are notsetting at the distal or proximal ends of the movement limiting means24, thus increases blade efficiency.

[0067] Thus, in each of the embodiments described above, movement of theblades 8 from the first position ‘A’ to the second position ‘B’ movesthe blades from a higher drag orientation to a much lower dragorientation in the fluid, to provide for a reduction in the energy lossexhibited by the prime mover in converting the linear fluid flow intorotational movement.

[0068] Referring to FIGS. 10A-10G, the shape of the blades 8 isimportant in order to affect a higher drag in the first position thanthe second position. Preferred blade shapes include wedge-shaped,whether rounded, as shown in FIG. 10A, angular as shown in FIG. 10D,rectangular parallelepiped-shaped as shown in FIGS. 10B (rounded ends)and 10D (angular ends), blades having a kite-shaped cross-section asshown in FIG. 10E, airfoil-shaped as shown in FIG. 10F, andairfoil-shaped with trim tab attached as shown in 10G. Preferred bladeshape of blades 8 could either be with or without trim tabs partly orcompletely spanning along the blade 8 trailing edge or blade tip 22.

[0069] The reader's attention is directed to all papers and documentswhich are filed concurrently with or previous to this specification inconnection with this application and which are open to public inspectionwith this specification, and the contents of all such papers anddocuments are incorporated herein by references. All of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), and/or all of the steps of any method or processso disclosed, may be combined in any combination, except combinationswhere at least some of such features and/or steps are mutuallyexclusive.

[0070] Each feature disclosed in this specification (including anyaccompanying claims, abstract and drawings), may be replaced byalternative features serving the same, equivalent, or similar purpose,unless expressly stated otherwise. Thus, unless expressly statedotherwise, each feature disclosed is one example only of a genericseries of equivalent or similar features.

[0071] The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstracts and drawings), or to any novel one,or any novel combination, of the steps of any method or process sodisclosed.

1. A prime mover (2) for harnessing energy from flow of a fluid, theprime mover comprising a shaft (4) having a rotational axis, arranged tobe rotatably mounted to a substructure, the shaft comprising at leastone arm (6) extending radially from the shaft (4), the or each arm (6)comprising at least one blade (a), wherein the or each blade (8) isoriented such that fluid flow acting on the ox each blade (8) effectsrotation of the shaft (4), characterised in that the or each blade (8)is movably mounted on an arm (6) and wherein each blade is movable froma first position, having a first drag, to a second position, having asecond drag, wherein the first drag is higher than the second drag, andwherein the or each blade is provided with a trim tab, attached to orintegral with the blade and partly or completely spanning blade tip orthe trailing edge of the blade.
 2. A prime mover (2) as claimed in claim1, wherein the or each blade (8) is airfoil-shaped.
 3. A prime mover (2)as claimed in claim 1 or 2, wherein the flow of fluid effects movementof the or each blade (8) from the first to the second position as theshalt (4) is rotated.
 4. A prime mover (2) as claimed in any of claims 1to 3, wherein the surface area of the or each blade (8) impinged on bythe fluid is greater in the first position than in the second position.5. A prime mover (2) as claimed in any preceding claim, wherein the flowof fluid effects movement of the or each blade (8) from the secondposition back to the first position as the shaft (4) completes a fullrotation.
 6. A prime mover (2) as claimed in any preceding claim,wherein the prime mover (2) comprises at least two arms (6), and atleast one blade (8) is in the second position when at least one otherblade (8) is in the first position.
 7. A prime mover (2) as claimed inany preceding claim, wherein each blade (8) and/or arm (6) comprisesmeans is (16) to limit movement of each blade (8) on an arm (6) to aprescribed amount.
 8. A prime mover (2) as claimed in any precedingclaim, wherein each blade (8) is rotatably mounted to an arm (6) suchthat the blade (8) may be rotated from the first to the second position.9. A prime mover (2) as claimed in any preceding claim, wherein each armand or blade comprises means (24) to prevent each blade (a) movingbetween the first and second positions until the shaft (4) has rotated aprescribed distance.
 10. A crime mover (2) as claimed in any precedingclaim, wherein each arm and or blade comprises means (24) to limitmovement of each blade (8) on an arm (6) to a prescribed angulardisplacement of the blade (8) with reference to the corresponding arm(6).
 11. A prime mover (2) as claimed in claim 1, wherein each arm (6)comprises more than one blade (B), each blade (8) being movably mountedon the arm (6).
 12. A prime mover (2) as claimed in any preceding claim,wherein the prime mover (2) is arranged to be rotatably mounted to anysuitable sub-structure, such as an energy generating apparatus.
 13. Anenergy-generating device comprising a prime mover as claimed in anypreceding claim, connected to an energy generating apparatus.
 14. Amethod of generating energy from flow of a fluid, the method comprisingmounting the prime mover (2) as claimed in any preceding claim, to asuitable energy-generating device, and locating the resultant apparatusin a flow of fluid.
 15. A method as claimed in claim 14, wherein theprime mover (2) is oriented in the flow of fluid such that therotational axis of the shaft (4) is oriented substantially verticallywith respect to ground level and the arms (6) extend radiallysubstantially horizontally with respect to ground level.
 16. A method asclaimed in claims 14 or is, wherein the prime mover (2) mounted to theenergy generating apparatus is located in the flow of any fluid, air orwater.